runtime/debug: add GoVersion to BuildInfo

BuildInfo now includes the version of Go used to build a binary, as
reported by runtime.Version() or 'go version'.

For #37475

Change-Id: Id07dda357dc70599d64a9202dab894c7288de1de
Reviewed-on: https://go-review.googlesource.com/c/go/+/353888
Trust: Jay Conrod <jayconrod@google.com>
Run-TryBot: Jay Conrod <jayconrod@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

api/next.txt

@@ -3,6 +3,7 @@ pkg debug/buildinfo, func ReadFile(string) (*debug.BuildInfo, error)
 pkg debug/buildinfo, type BuildInfo = debug.BuildInfo
 pkg runtime/debug, method (*BuildInfo) MarshalText() ([]byte, error)
 pkg runtime/debug, method (*BuildInfo) UnmarshalText() ([]byte, error)
+pkg runtime/debug, type BuildInfo struct, GoVersion string
 pkg syscall (darwin-amd64), func RecvfromInet4(int, []uint8, int, *SockaddrInet4) (int, error)
 pkg syscall (darwin-amd64), func RecvfromInet6(int, []uint8, int, *SockaddrInet6) (int, error)
 pkg syscall (darwin-amd64), func SendtoInet4(int, []uint8, int, SockaddrInet4) error

src/cmd/go/internal/load/pkg.go

@@ -2200,6 +2200,9 @@ func (p *Package) collectDeps() {
 // setBuildInfo should only be called on a main package with no errors.
 //
 // This information can be retrieved using debug.ReadBuildInfo.
+//
+// Note that the GoVersion field is not set here to avoid encoding it twice.
+// It is stored separately in the binary, mostly for historical reasons.
 func (p *Package) setBuildInfo() {
 	setPkgErrorf := func(format string, args ...interface{}) {
 		if p.Error == nil {

src/debug/buildinfo/buildinfo.go

@@ -71,7 +71,7 @@ func ReadFile(name string) (info *BuildInfo, err error) {
 // accessed through the given ReaderAt. Most information is only available for
 // binaries built with module support.
 func Read(r io.ReaderAt) (*BuildInfo, error) {
-	_, mod, err := readRawBuildInfo(r)
+	vers, mod, err := readRawBuildInfo(r)
 	if err != nil {
 		return nil, err
 	}
@@ -79,6 +79,7 @@ func Read(r io.ReaderAt) (*BuildInfo, error) {
 	if err := bi.UnmarshalText([]byte(mod)); err != nil {
 		return nil, err
 	}
+	bi.GoVersion = vers
 	return bi, nil
 }
 

src/debug/buildinfo/buildinfo_test.go

@@ -142,7 +142,8 @@ func TestReadFile(t *testing.T) {
 		{
 			name:  "valid_modules",
 			build: buildWithModules,
-			want: "path\texample.com/m\n" +
+			want: "go\t$GOVERSION\n" +
+				"path\texample.com/m\n" +
 				"mod\texample.com/m\t(devel)\t\n",
 		},
 		{
@@ -157,7 +158,7 @@ func TestReadFile(t *testing.T) {
 		{
 			name:  "valid_gopath",
 			build: buildWithGOPATH,
-			want:  "",
+			want:  "go\t$GOVERSION\n",
 		},
 		{
 			name: "invalid_gopath",
@@ -193,7 +194,7 @@ func TestReadFile(t *testing.T) {
 						} else if got, err := info.MarshalText(); err != nil {
 							t.Fatalf("unexpected error marshaling BuildInfo: %v", err)
 						} else {
-							got := string(got)
+							got := strings.ReplaceAll(string(got), runtime.Version(), "$GOVERSION")
 							if got != tc.want {
 								t.Fatalf("got:\n%s\nwant:\n%s", got, tc.want)
 							}

src/runtime/debug/mod.go

@@ -7,6 +7,7 @@ package debug
 import (
 	"bytes"
 	"fmt"
+	"runtime"
 )
 
 // exported from runtime
@@ -25,14 +26,22 @@ func ReadBuildInfo() (info *BuildInfo, ok bool) {
 	if err := bi.UnmarshalText([]byte(data)); err != nil {
 		return nil, false
 	}
+
+	// The go version is stored separately from other build info, mostly for
+	// historical reasons. It is not part of the modinfo() string, and
+	// ParseBuildInfo does not recognize it. We inject it here to hide this
+	// awkwardness from the user.
+	bi.GoVersion = runtime.Version()
+
 	return bi, true
 }
 
 // BuildInfo represents the build information read from a Go binary.
 type BuildInfo struct {
-	Path string    // The main package path
-	Main Module    // The module containing the main package
-	Deps []*Module // Module dependencies
+	GoVersion string    // Version of Go that produced this binary.
+	Path      string    // The main package path
+	Main      Module    // The module containing the main package
+	Deps      []*Module // Module dependencies
 }
 
 // Module represents a module.
@@ -45,6 +54,9 @@ type Module struct {
 
 func (bi *BuildInfo) MarshalText() ([]byte, error) {
 	buf := &bytes.Buffer{}
+	if bi.GoVersion != "" {
+		fmt.Fprintf(buf, "go\t%s\n", bi.GoVersion)
+	}
 	if bi.Path != "" {
 		fmt.Fprintf(buf, "path\t%s\n", bi.Path)
 	}
@@ -116,7 +128,7 @@ func (bi *BuildInfo) UnmarshalText(data []byte) (err error) {
 		line []byte
 		ok   bool
 	)
-	// Reverse of BuildInfo.String()
+	// Reverse of BuildInfo.String(), except for go version.
 	for len(data) > 0 {
 		line, data, ok = bytes.Cut(data, newline)
 		if !ok {